1. Field of the Invention
The present invention relates to a sheet processing apparatus, and more particularly, to a sheet processing apparatus which is used in an image forming apparatus, such as a copier, a laser-beam printer or the like, and which performs processing, such as sorting, binding and the like, for sheets discharged from the image forming apparatus.
2. Description of the Related Art
In some apparatuses for conveying, mounting and sorting sheets discharged from an image forming apparatus or the like, in order to prevent degradation in the processing capability due to sheet processing at the downstream side requiring a relatively long processing time, such as a bundle-binding operation, a portion where a sheet is temporarily stopped is provided at a conveying portion, in order to temporarily interrupt conveyance of the sheet. Thereafter, a plurality of sheets are conveyed together with another sheet conveyed from the upstream side, in order to secure a time for sheet processing at the downstream side and prevent a decrease in the overall efficiency of sheet processing. In some of such apparatuses, when the system enters a non-operating state due to a sheet jam or the like, in order to prevent occurrence of curl of a sheet to a degree more than necessary and prevent the sheet from remaining within the apparatus from the viewpoint of maintenance of the system, the sheet is automatically discharged when the sheet is present at a temporarily stopped portion.
However, an apparatus in which a sheet is automatically discharged when the system is operating and the sheet is present at a temporarily stopped retracted portion is not present.
In the above-described situation, problems may arise, such as a failure in sheet conveyance or sheet alignment due to simultaneous conveyance of sheets having different conveying speeds in a superposed state.
Furthermore, when there is a sheet which is temporarily stopped in order to perform the above-described processing, there is a problem such that another sheet cannot be conveyed to the conveying path for the stopped sheet or to another portion requiring driving for a portion for conveying the stopped sheet.